Techniques for delivering pulsed wireless power

ABSTRACT

A transmitter assembly is useful in optimizing the delivery of wireless power to a plurality of receivers. Each receiver measures its own battery need for power and transmits that measurement as a request to the transmitter. The transmitter is configured to normalize and compare battery need requests. The transmitter then allocates pulses of wireless power among the requesting receivers according to their battery need.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/367,900 filed on Dec. 2, 2016, and issued asU.S. Pat. No. 10,312,744 on Jun. 4, 2019; which is a continuation of andclaims priority to U.S. patent application Ser. No. 14/171,750 filed onFeb. 3, 2014, and issued U.S. Pat. No. 9,553,473 on Jan. 24, 2017; whichclaims priority to and benefit from U.S. Provisional Patent ApplicationNo. 61/760,648 filed on Feb. 4, 2013, each of which are expresslyincorporated by reference herein.

BACKGROUND

Many useful applications are based on the transmission of wirelesspulses. Examples include radar detection using transmitted and reflectedpulsed microwave signals as well as medical ablation procedures that usepulsed microwave to ablate targeted body tissues.

Concerning pulsed signals used to deliver power wirelessly, the companyPowercast filed patent application US20070149162 in January 2007. Thatapplication discusses pulsing in order to optimize the delivery ofwireless power.

The above patent application (US20070149162) discusses certainadvantages of pulsing for wireless power delivery, including:

-   -   Increased rectifier efficiency;    -   Larger output voltages; and    -   Less average transmitted power used to obtain the same received        DC power.

Transmitting less average power has the following advantages:

-   -   Decreasing the human safety distance;    -   Allowing operation in an increasing number of bands;    -   Recharging at a lower average output than continuous wave power        transmission; and    -   Greater distances of higher power levels, as well as penetration        of RF-attenuating objects without increasing the average output        power.

However, US20070149162 fails to disclose the unique challenges posed bydelivering power wirelessly, and thus does not address solutions tothese unique challenges. These challenges include:

-   -   Sequential delivery;    -   Attenuation of reception;    -   Variable state of charge; and    -   Storage drain rate.

Each of these challenges is described below.

Sequential delivery refers to the fact that in wireless power systems,typically most or all of the power generated by the transmitter isdelivered to one or a few receivers at a time. One reason is becausesignal strength drops significantly with distance due to theinverse-square law (the intensity of the signal falls off proportionallyto the square of the distance). This means that at any one time, most orall of the transmitter power is preferentially delivered to only one ora few receivers.

Attenuation of reception references the fact that the strength of apower signal received by a receiver can be diminished by variousfactors, including distance from transmitter, obstacles betweentransmitter and receiver, and orientation of receiver.

Variable state of charge concerns the state of the charge-holdingapparatus in the receiver. Normally, this apparatus is a battery, but itcould also be a capacitor. This charge-holding device exhibits a stateof charge ranging from empty to full.

Storage drain rate concerns the rate at which the charge-holdingapparatus (e.g. battery) is losing charge.

This invention describes solutions to these core problems of wirelesspower delivery.

SUMMARY

In accordance with the present invention, systems and methods foroptimally delivering pulsed wireless power using a transmitter assemblythat is useful in optimizing the delivery of wireless power to aplurality of receivers is provided. Each receiver measures its ownbattery need for power and transmits that measurement as a request tothe transmitter. The transmitter is configured to normalize and comparebattery need requests. The transmitter then allocates pulses of wirelesspower among the requesting receivers according to their battery need.

Note that the various features of the present invention described abovemay be practiced alone or in combination. These and other features ofthe present invention will be described in more detail below in thedetailed description of the invention and in conjunction with thefollowing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be more clearly ascertained,some embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 shows a high level block diagram demonstrating a wirelesstransmitter and multiple receivers;

FIG. 2A depicts a circuit configured to calculate a state of charge of abattery;

FIG. 2B depicts a circuit configured to calculate a power drain rate ofthe battery;

FIG. 3 depicts a circuit configured to calculate a received power by thebattery;

FIG. 4 depicts an alternative circuit configured to calculate thereceived power by the battery;

FIG. 5 depicts a circuit configured to calculate the state of charge,the power drain rate, and the received power by the battery;

FIG. 6 depicts a circuit configured to detect if the battery is overcharged;

FIG. 7 depicts a sequence of pulses for a transmitter communicating withmultiple receivers;

FIG. 8 shows a sequence of power pulses forming a power burst;

FIG. 9 shows an example of a transmitter-receiver communication scheme,in which no receivers are detected by the transmitter;

FIG. 10 shows an example of a transmitter-receiver communication scheme,in which one receiver is detected by the transmitter;

FIG. 11 shows an example of a transmitter-receiver communication scheme,in which the detected receiver by the transmitter is recognized as anauthorized receiver;

FIG. 12 shows an example of a transmitter-receiver communication scheme,in which the authorized receiver is receiving wireless power; and

FIG. 13 depicts an example of a transmitter-receiver communicationscheme, with the transmitter recognizing and supplying power to at leasttwo receivers.

DETAILED DESCRIPTION

The present invention will now be described in detail with reference toseveral embodiments thereof as illustrated in the accompanying drawings.In the following description, numerous specific details are set forth inorder to provide a thorough understanding of embodiments of the presentinvention. It will be apparent, however, to one skilled in the art, thatembodiments may be practiced without some or all of these specificdetails. In other instances, well known process steps and/or structureshave not been described in detail in order to not unnecessarily obscurethe present invention. The features and advantages of embodiments may bebetter understood with reference to the drawings and discussions thatfollow.

Aspects, features and advantages of exemplary embodiments of the presentinvention will become better understood with regard to the followingdescription in connection with the accompanying drawing(s). It should beapparent to those skilled in the art that the described embodiments ofthe present invention provided herein are illustrative only and notlimiting, having been presented by way of example only. All featuresdisclosed in this description may be replaced by alternative featuresserving the same or similar purpose, unless expressly stated otherwise.Therefore, numerous other embodiments of the modifications thereof arecontemplated as falling within the scope of the present invention asdefined herein and equivalents thereto. Hence, use of absolute and/orsequential terms, such as, for example, “will,” “will not,” “shall,”“shall not,” “must,” “must not,” “first,” “initially,” “next,”“subsequently,” “before,” “after,” “lastly,” and “finally,” are notmeant to limit the scope of the present invention as the embodimentsdisclosed herein are merely exemplary.

The present invention concerns systems and methods of pulsed wirelesspower transmission and reception. FIG. 1 shows a high level blockdiagram 1 demonstrating a transmitter 2 transmitting wirelesscommunications 3 as well as wireless power 4. A plurality of receivers 5a, 5 b, 5 c, . . . 5 n communicates with the transmitter 2 throughwireless signals 6 a, 6 b, 6 c, . . . 6 n respectively. Receivers 5 a, 5b, 5 c, . . . 5 n collect needed wireless power 7 a, 7 b, 7 c, . . . 7 ntransmitted by the transmitter 2.

Pulsing of the wireless power signal facilitates sequential delivery inthat individual pulses can be allocated to different receivers bychanging any of phase, frequency, time, amplitude, or direction of atransmitter. Although the detailed description herein concerns phasefocused pulsing, this invention is equally applicable to any othersignal modification approach.

Moreover, the description below describes the delivery of pulses to onereceiver at a time. But this invention includes approaches that involvepowering a subset of receivers at a time. For example, in a frequencymodulated pulsing approach, some subset of receivers might be tuned toreceive a certain frequency. When the transmitter delivers a pulse ofthat frequency, this subset of more than one receiver would besimultaneously charged.

In one embodiment of the described invention, the delivery of wirelesspower by a transmitter to a plurality of receivers is disclosed. Thediscussion below concerns batteries as the means of charge storage forthese receivers. But this invention applies equally to any means ofcharge storage, including capacitors and super-capacitors.

Moreover, beyond battery needs for power, some receivers might have amore critical/urgent need for power than other receivers. For example,life-preserving receivers (for example, a heart pump) would have a morecritical need for power than non-critical ones (for example, a toy)—aneed that is independent of the respective battery power needs of thetwo devices.

One embodiment of the described invention concerns variable batteryneeds. Satisfying variable battery needs of one or more receiversinvolves the following functions:

-   -   Measuring battery need;    -   Communicating battery need;    -   Receiving battery need; and    -   Satisfying battery need.

In measuring battery need there are multiple schemes that receivers useto determine their needs before sending them to the transmitter. Theseschemes range from simple measurements of voltages and currents, tosophisticated calculations. Some of the latter can even be predictive,presenting estimations about expected conditions in the future anddetermining amounts of power such that those anticipated needs will befilled should they occur.

The receiver must take various measurements and, in some embodiments,make various calculations before it can send the needed information tothe transmitter.

Electronic circuits located within or associated with the receivermeasure core metrics required for calculating battery need. Threecontinuously varying metrics (the “Battery Need Metrics”) useful formeasuring battery need are:

-   -   State of charge (“StateOfCharge”) which describes how the        battery is charged;    -   Drain rate (“DrainRate”) which describes how fast the battery        charge is draining;

and

-   -   Received power (“ReceivedPower”) which describes how much power        the battery is receiving.

All things being equal between two batteries, one of them will have agreater need for power if:

-   -   Its StateOfCharge is lower than that of the other;    -   Its DrainRate is higher than that of the other; or    -   Its ReceivedPower is lower than that of the other.

For a typical battery, each of the three Battery Need Metrics tends tovary relatively frequently (e.g. within seconds or fractions of asecond).

Electronic circuits within the receiver measure some or all of theBattery Need Metrics. The discussion below describes alternativeembodiments of these circuits.

The first of these embodiments discloses an individual circuit for eachmetric. FIG. 2A depicts a circuit 10 configured to calculate theStateOfCharge of a battery. In the circuit 10, a voltage supply 11represents a received power that charges a battery 12. The battery 12 isconnected through a resistor 13 to an Operational Amplifier (“OpAmp”)14. A second resistor 15 sets the gain of the OpAmp 14. The OpAmppositive “+” terminal is connected to a voltage reference (“VREF”) 16that can be set in at least two ways.

In a first way of the at least two ways of setting the voltage reference(VREF) 16, its voltage is set higher than the highest expected voltagevalue for the battery. This will make the OpAmp 14 produce a range ofpositive values for an Analog-to-Digital Converter (“ADC”) 17 regardlessof the battery's state of charge. The ADC 17 digitizes the signal fromthe OpAmp 14 and presents 8 bits of data to a Microprocessor 18. TheMicroprocessor 18 can be configured to generate a table 19 listing thebattery voltage and the percentage full of the battery.

In a second way of the at least two ways for setting the voltagereference (VREF) 16, its voltage is set to match a voltage valueslightly higher than that which the battery will reach when it can nolonger safely provide power. This changed sign is an easily testedcondition by the Microprocessor 18, and may make the software easier towrite.

FIG. 2B depicts a circuit 20 configured to calculate the DrainRate of abattery. The circuit 20 comprises a Device Electronics 22 with the “+”power terminal connected to a voltage supply 21 that represents thereceived power, and the “−” power terminal connected to two resistors 23and 25 and an OpAmp 24. The two resistors 23 and 25 set the gain of theOpAmp 24.

The resistor 23 connects the positive“+” and the negative “−” inputterminals of the OpAmp 24 together, and has a very low resistance (forexample, on the order of one to five milli Ohms).

The resistor 25 connects the negative “−” input of the OpAmp 24 to theoutput terminal of the OpAmp 24. The OpAmp 24 output signal is connectedto the input of an ADC 27. The ADC 27 digitizes the signal from theOpAmp 24 and presents 8 bits of data to a Microprocessor 28.

The resistor 25 should be selected so that the maximum expected powerdraw (by the Device Electronics 22) causes an output voltage from theOpAmp 24 near the maximum value that the ADC 27 input stage can read.

ReceivedPower can be calculated using a circuit 30 depicted in FIG. 3.An antenna 31 is connected to the primary of a transformer 32. Thesecondary of the transformer 32 is connected to the rectifying diodes 36and a capacitor 39. A voltage across the capacitor 39 is essentially DC(direct current with some ripple) and is configured to be proportionalto the power being received by the antenna.

An alternative embodiment for calculating the ReceivedPower is shown inFIG. 4. The circuit 40 is configured to measure both the current flowinginto the “Device Electronics” 22 in addition to the voltage across thecapacitor 39. The analog voltage at point A, “V_(A)” is proportional tothe current flowing into the “Device Electronics” 22. The analog voltageat point B, “V_(B)” is proportional to the voltage across the capacitor39. The analog voltages V_(A) and V_(B) are multiplied in a mixer 47.Thus, the output voltage of the mixer 47 at point C, “V_(C)” isproportional to the power being received by the antenna. The voltageV_(C) is digitized in the ADC 37 and then fed to the microprocessor 18.The circuit 40 thus can be configured to provide the power, in watts,being delivered wirelessly to the receiver.

In yet another embodiment for measuring the ReceivedPower, the analogvoltages V_(A) and V_(B), in FIG. 4, can be digitized using twoAnalog-to-Digital Converters (ADCs), not shown. Then the output of thetwo ADCs can be easily multiplied digitally and the digitized result ismade available to the microprocessor 18.

In an alternative embodiment, a single electronic circuit can beconfigured to measure all three of the Battery Need Metrics. Thisembodiment makes six measurements (the “Raw Metrics”):

-   -   V[RF] (volts from RF)    -   A[RF] (amps from RF)    -   V[S] (volts at storage)    -   A[S] (amps at storage)    -   V[D] (volts at device)    -   A[D] (amps at device)

The six Raw Metrics are measured using the circuit 50, depicted in FIG.5. A rectifying antenna (rectenna) 51 feeds power to a Storage Cell 52(e.g., battery) through ammeter A[RF] 53. The Storage Cell feeds powerto the Device Electronics 22 through ammeters A[S] 55 and A[D] 57.Voltmeter V[RF] 54 measures the voltage at the smoothed output of therectenna 51, voltmeter V[S] 56 measures the voltage across the StorageCell 52, and voltmeter V[D] 58 measures the voltage across the DeviceElectronics 22.

Preferentially, each of these six measurements is takencontemporaneously enough to minimize errors due to time delays betweenrelated, fluctuating voltage and current readings when they aremultiplied together.

Once these six Raw Metrics measurements have been taken, calculationsare executed to obtain the Battery Need Metrics. First, DrainRate iscalculated as:DrainRate=A[D]

ReceivedPower can be derived by multiplying the voltage and currentcoming from the Rectenna as follows:ReceivedPower=W[RF]=V[RF]*A[RF]

The third Battery Need Metric—StateOfCharge—is a numerical percentage oftotal storage device capacity. This metric can be measured in multipleways.

In the first way, StateOfCharge can be derived by observing theslightly-varying voltage of the storage device and using a lookup-tableto find the SOC value:StateOfCharge˜=f{V[S]}

In a second way, StateOfCharge can be determined by continually summingthe instantaneous currents supplied to (or removed from) the storagedevice and applying appropriate correction factors. This is known in theart as “Coulomb counting”:StateOfCharge˜=g{Sum(A[S])}

Both of the first two methods of measuring StateOfCharge have well-knowndifficulties, which are the subject of continuing research andrefinements. In either case, the StateOfCharge is transformed into aunit-less number—a percentage of the entire charge capacity of thedevice.

If the A[S] measurement is not provided, one of the drawbacks of havingonly V[S] is that a lookup table provides accurate values only for“no-load” conditions, after the battery has had a period of rest. Withthe additional ammeter, the second formula(StateOfCharge˜=g{Sum(A[RF]−A[D])}) can be replaced by the followingformula: StateOfCharge˜=h{Sum(V[S]*A[S])}

Note that the function g{ } provides Amperes, and the function h{ }provides Watts or Watt*seconds—dependent on how h{ } is calculated.

In addition to the continuously varying Battery Need Metrics, someembodiments of this invention also make use of slower varying metrics.These latter metrics include storage capacity and maximum charge rate(the “Battery Rating Metrics”).

The storage capacity (“StorageCapacity”) of a battery concerns themaximum charge the battery can hold. This metric is used to computeStateOfCharge of the battery. StateOfCharge can be expressed as apercentage of StorageCapacity. StorageCapacity is typically measured inAmpere*Hours. Attempts to charge a battery beyond the ratedStorageCapacity usually generate heat, and in some cases damage thebattery.

In addition to storage capacity, batteries have a maximum charge rate(“MaxChargeRate”), which is a measure of how fast the battery canassimilate charge. Pushing too much energy into a battery over too shorta time frame can damage the battery. MaxChargeRate can be measured inWatt*seconds (Joules) per second, which is equivalent to Watts (i.e.W*s/s=W).

StorageCapacity vary widely among batteries. Moreover, batteries aretypically rated with a static StorageCapacity. These rates arecalculated and published by the manufacturers of the batteries.Manufacturers typically publish graphs showing how these readingsdecline over time.

As with StorageCapacity, MaxChargeRate is typically expressed as astatic rating of the battery, with manufacturers providing data sheetsshowing how this rating typically declines over time.

One embodiment of this invention uses these manufacturer-provided staticratings of StorageCapacity and MaxChargeRate.

However, one preferred embodiment calculates the Battery Rating Metricsdirectly. This is because the actual performance of batteries on thesemetrics can vary from the static rating due to inefficient rechargingpractices. But this variance (usually a reduction) in batteryperformance typically occurs over a time-frame much longer than seconds(e.g. weeks, months, and even years).

Today, measurements for the Battery Rating Metrics are generally nottaken on storage devices found in equipment being used.

A direct way to detect when MaxChargeRate is exceeded can be useful.FIG. 6 depicts an electronic circuit 60 that can be configured to detectwhen MaxChargeRate of a battery 61 is exceeded. Two thermistors A 62 andB 63 are employed. The thermistor is a type of resistor the resistanceof which varies significantly with temperature, more so than withstandard resistors. Thermistors are widely used as current-limitingdevices for circuit protection.

The thermistor A 62 is exposed to ambient temperature, while thethermistor B 63 is in close contact with the battery 61. When thebattery 61 heats up because it is being overcharged, the heat produced,would change the resistance of thermistor B 63 and hence change theresulting voltage across B 63. A comparator circuit 64 detects thedifference in the resulting voltages across the thermistors A 62 and B63 and generates an analog voltage V_(C) at point C which is fed to anADC 65 to digitize the analog voltage output V_(C) of the comparatorcircuit 64. The digitized signal is then fed to a microprocessor 18. Toensure that the thermistor B 63 is in close contact with the battery 61,a cylindrical clamp 66 can be used to hold the thermistor B 63 againstthe battery 61. A blot 67 can be used to tighten the clamp 66 around thebattery 61.

A binary value “being overcharged” is ambiguous: either meaning“MaxChargeRate being exceeded” or “Being charged to more than 100%StorageCapacity”. However, both meanings are useful. (Batteries alsooverheat if they are discharged too quickly—but it is easy to determineif they are being charged or discharged by examining the sign ofDrainRate—negative being charging, and positive being discharging.)

Once the Battery Need Metrics are measured and converted into digitalrepresentations, Momentary Battery Need can be calculated. MomentaryBattery Need is a single metric representing current battery need.

Let function ƒ represent Momentary Battery Need, and variables s, d, andr represent StateOfCharge, DrainRate, and ReceivedPower, respectively.Then the function ƒ(s,d,r) is Momentary Battery Need.

Some constraints on the function ƒ(s,d,r) include the following: For tworeceivers, and for the same receiver over two measurements;

with equal d and r, ƒ is higher for the one with the lowers;

with equal d and s, ƒ is higher for the one with the lower r; and

with equal r and s, ƒ is higher for the one with the higher d

A practical alternative to the theoretical function ƒ is “Time to Die”(“TTD”). TTD is a measurement of the time predicted for which thestorage device will continue to provide energy at present levels. Afterthat time, the storage device is predicted to exhaust all the energy ithas stored. At that time, the dependent electronic device no longerreceives energy, so it will cease to function (or in the vernacular,“die”).

In calculating TTD, the intent is to take the remaining charge of thestorage cell (or battery) (“RemainingCharge”) and divide it by theDrainRate, and thereby obtain the time period before which exhaustionoccurs, the TTD:TTD=RemainingCharge(As)/DrainRate(A)=A*s/A=s

RemainingCharge is computed from StateOfCharge (a percentage) andStorageCapacity, typically measured in Ampere Hours (A*h or Ah), andeasily convertible to Ampere Seconds (A*s or As):RemainingCharge(As)=StateOfCharge(%)*StorageCapacity(Ah)*3600

Accordingly, the TTD parameter estimates the number of seconds thestorage device can support the present power draw level.

Over time, multiple readings of TTD for each receiver satisfy the sameconstraints on the negative of function ƒ (i.e. −ƒ) as described above.

For another example of calculating Momentary Battery Need, any of thethree Battery Need Metrics can serve as a rough estimate. That is,Momentary Battery Need could equal StateOfCharge, DrainRate, orReceivedPower.

One reason for using any of the foregoing Battery Need Metrics insteadof TTD is to simplify the measuring electronic circuitry required withinthe receiver.

Under one embodiment of this invention, different receivers can employdifferent battery need measurements. Some receivers might employ TTD,others one of the Battery Need Metrics, and still others, might useanother variant based on the Battery Need Metrics.

Momentary Battery Need can provide an inaccurate reading of true need.This is because, from moment to moment, Momentary Battery Need can varysignificantly.

Accordingly, a preferred embodiment of this invention calculates aSmoothed Battery Need that is a calculation based on multiple readingsof Momentary Battery Need.

For example a MovingAverage can smooth fluctuating Momentary BatteryNeed readings out and provide a Smoothed Battery Need. An examplesmoothing algorithm for MovingAverage can be expressed as a series ofsteps to calculate the smoothed result for each successive reading:Total=Total−Reading(This)Reading(This)=NewReadingTotal=Total+Reading(This)This=Next(This)Return(Total/Count)

This presumes that “Count” contains the number of items in the movingaverage range; that the first “Count” generated results are discarded;and that the “Next” function is aware of “Count” and sets “This” back tothe start of the “Reading” array after “This” reaches the end of the“Reading” array.

In the example above, Return (Total/Count) equals Momentary BatteryNeed. e.g., Momentary TTD. So the value returned by the algorithm isSmoothed Battery Need. e.g., Smoothed TTD.

The foregoing describes only one smoothing function. But manyalternative smoothing functions are known in the art. This invention canuse any such smoothing function.

Another consideration in measuring true battery need is that a historyof battery drain rates for a receiver can be useful for predicting thefuture need. With this approach, the immediate prior “Return(Total/Count)” readings like that used for calculating Smoothed BatteryNeed is not enough. For predicting battery need, the prior readingspreferentially can span weeks or months, not merely seconds or minutes,in order to discern useful patterns.

Historical data for a receiver is preferentially stored in thatreceiver. This is because if that receiver's history is kept in thewireless power transmitter serving it, then that transmitter will haveonly partial records of its history available if the receiver movesamong different transmitters over the course of days (e.g., a mobilephone moving from home to the car to an office to a restaurant back tothe office back to the car back to home, with some or all of thoselocales hosting a transmitter that charges the phone).

The time to start predicting the future is the moment when wirelesspower becomes available to the receiver again. A wireless power“Session” is the duration between the time when wireless power becomesavailable to a receiver, and the next time wireless power becomesavailable—including the intervening time when wireless power was notavailable. The Session starts when power becomes available to fulfill apredicted need, and the prediction calculation should be startedconcurrently.

For each Session, “Session Data” is collected characterizing theSession. An example of such data is below:

Session Data

StartTimeStamp HHMMSS DayOfWeek 1-7 SessionDuration secondsPowerAvailableDuration seconds ReceivedPowerLevelAverage WTotalEnergyDrain Ws

StartTimeStamp is the start of the Session. DayOfTheWeek is the day onwhich the Session StartTimeStamp started. SessionDuration is the lengthof time during which the Session lasted.

PowerAvailableDuration is the length of time during which ReceivedPower(V[RF]*A[RF]) is greater than zero.

ReceivedPowerLevelAverage is the average of ReceivedPower during theSession. This is computed by summing, over the Session, periodicrecordings of ReceivedPower into ReceivedPowerLevel, and dividing thelatter by PowerAvailableDuration.

TotalEnergyDrain is the accumulated sum of DrainRate (V[D]*A[D])multiplied by the SessionDuration yielding WattSeconds (Ws).

After a sufficient number of “Session Data” records have beenaccumulated, it will be possible to find Session Data records withStartTimeStamp values that are near the present system time when theprediction needs to be made. All records matching that criterion canhave averages, medians, or means (or other statistical parameters)calculated (possibly by taking into account DayOfWeek) in order toprovide the following parameters:

TypicalSessionDuration seconds TypicalPowerAvailableDuration secondsTypicalReceivedPowerLevelAverage W TypicalTotalEnergyDrain Ws (for theentire session)

These parameter names starting with “Typical” are used to predict thefuture based on past conditions. These parameters (and possibly others)are used to derive useful metrics:PredictedEnergyNeed(Ws)=TypicalTotalEnergyDrain(Ws)PredictedEnergyReceived(Ws)=TypicalReceivedPowerLevelAverage(W)*TypicalPowerAvailableDuration(s)

These metrics can be used to calculate how many seconds the receiverneeds to stay where it can receive wireless power. With suitablecalculations, predictions based on earlier similar sessions could allowthe transmitter to email the receiver a warning. An example of thewarning can be:

-   -   You may be planning to leave an area providing wireless power        earlier than recommended. Your iPhone's power is predicted to        last until about 10 PM with your typical usage. If you can        remain and draw more wireless power for 9 more minutes, you can        extend this time to 11 PM. Sent from your wireless power cell.

This email could be generated in this way:

TOD is Time Of Day AdditionalEnergyNeed (Ws) = PredictedEnergyNeed (Ws)− PredictedEnergyReceived (Ws) If AdditionalEnergyNeed > 0 ThenBatteryEnergy (Ws) = StateOfCharge(%) * StorageCapacity (Ws)PredictedNoPowerDuration (s) = TypicalSessionDuration (s) −TypicalPowerAvailableDuration (s) PredictedFinalPowerDraw (W) =TypicalTotalEnergyDrain (Ws) / PredictedNoPowerDuration (s)BatteryRemainingSeconds (s) = BatteryEnergy (Ws) /PredictedFinalPowerDraw (W) WhenBatteryDies (TOD) = NowTimeStamp (TOD) +BatteryRemainingSeconds AdditionalTimeNeeded = AdditionalEnergyNeed /TypicalReceivedPowerAverage ExtendedTime (TOD) = StartTimeStamp +TypicalSessionDuration Email( userID, WhenBatteryDies,AdditionalTimeNeed, ExtendedTime); End If

BatteryRemainingSeconds can be used to serve as the value for PredictedTTD.

The foregoing discussion covered methods for measuring battery need. Inone embodiment of this invention, the only aspect of these methods thatmust be performed in the receiver are the electronic circuits formeasuring the need metrics.

For example, the electronic circuitry discussed for measuring each ofStateOfCharge, DrainRate, and ReceivedPower would be located in thereceiver. Similarly, the single circuit disclosed for measuring the RawMetrics (V[RF], A[RF], V[S], A[S], V[D], and A[D]) would be located inthe receiver.

But either the receiver or the transmitter can calculate MomentaryBattery Need, Smoothed Battery Need, or Predicted Battery Need.

Moreover, in the case of a plurality of receivers, different receiverscan calculate different need measurements. For example, one receivermight measure one of the Raw Metrics, Battery Need Metrics, MomentaryBattery Need, Smoothed Battery Need, and Predicted Battery Need(collectively, “Battery Need”). Other receivers might measure other waysof assessing Battery Need.

Once the receiver has calculated Battery Need, the next step is for thereceiver to communicate this information to the transmitter.

In one embodiment of this invention, this battery need information isencoded in a digital form, and transmitted wirelessly in a data packetby the receiver to the transmitter.

The representation of numbers in various bit and byte schemes hasdecades of history. Generally, for numbers that will be used withmathematical functions, it is necessary to know the range of the numbersthat will be encountered, and the accuracy desired for them. The numberof bits used in the encoding scheme affects both of these attributes.

The receiver generates and transmits a Battery Need Packet. This packetcontains information on the Battery Need of the receiver.

The Battery Need Packet is preceded by 1) a header containing startbytes, 2) a Receiver ID to identify which receiver is sending the data,and 3) a Message Type that indicates the Battery Need formula for thepacketized information.

In one embodiment, the packetized information is encrypted into a bytestream, and a modulator clocks the bytes out to the radio transmitter.The entire message is rendered as one series of bits.

One embodiment encodes the packet headers as follows:

Start bytes. These are a specific, unalterable series of bytes unlikelyto appear in real data. This allows an input scanner to continuallylooking for this sequence of bytes and thereby recognize the beginningof a data transmission. The number of bytes varies depending upon theimplementation, but is often in excess of 8 bytes.

Receiver ID bytes. This byte is assigned by the transmitter when thereceiver introduces itself.

Message Type: These bytes disclose the particular encoding scheme usedin the data section of the message. Two bytes would provide for wellover fifty thousand message types, again a more than adequate provision.In an embodiment in which different receivers measure Battery Need indifferent ways, Message Type also indicates which Battery Need formulawas used (e.g., Smoothed StorageCapacity).

In one embodiment, the data portion of the Battery Need Packet containsone or more of the three Battery Need Metrics.

ReceivedPower. For numbers relating to measurements appropriate forReceivedPower, we can expect a range of approximately 5 milliWatts (mW)to 5 Watts, or a range of about 1000. The accuracy the transmitter needscould tolerate being as far off as about 10 mW, so three significantdigits will be enough. If the measurements are encoded in 10 bits, theresult is three significant decimal digits, and 1024 unique values.Adding more bits can increase accuracy or range, or both, sorepresenting ReceivedPower measurements with 16 bit signed integers ismore than adequate, providing a range of values wider than −32 W through+32 W in 1 mW steps.

StateOfCharge. Due to the difficulties in deriving an accurateStateOfCharge value from battery voltage, the transmitter could get bywith a range of just 10 values, and 1 significant digit. In other words,a “Percent of Full Charge” range running from approximately 10% to 100%in 10% steps is state-of-the-art. This requires less than 4 bits ofinformation.

DrainRate. Numbers for DrainRate are likely in the range ofapproximately 0-500 mA, and need not be more accurate than discretesteps of about 1 mA. This is an approximate range of 500 values and anaccuracy of less than 3 significant digits. This requires less than 9bits of information.

In an embodiment, the receiver encodes all three of the foregoingmetrics. Once digitally encoded, the data is now packetized.

In one packetizing approach, 2 bytes is allocated to each of the threeBattery Need Metrics as follows:

Received Power 2 bytes State of Charge 2 bytes Drain Rate 2 bytes

These add up to 6 bytes total for the Battery Need information datapacket.

In an alternative packetizing approach, the three Battery Need Metricsare represented in their minimal bit patterns:

Received Power 10 bits State of Charge 4 bits Drain Rate 9 bits Total 23bits (or nearly 3 bytes).

The advantage of the second approach is a 50% reduction in data payloadsize. The disadvantage of this approach is slower computation at thetransmitter since the transmitter needs first to decode the 3 bytes intothe three metrics. No such decoding step is needed with the 6-bytepacket approach.

In another embodiment of this invention, the receiver encodes andpacketizes the Raw Metrics rather than the higher-order Battery NeedMetrics.

The voltages of the Raw Metrics will not, approximately, range as far as+/−30 volts, and resolving to the nearest millivolt is adequate.Therefore, 2-byte signed integers can be scaled to read from −32.767volts to +32.767 volts in one-millivolt steps.

The Raw Metrics currents will not, approximately, range as far as +/−3amps, and resolving to the nearest 100 microamps is adequate. Therefore,2-byte signed integers can be scaled to read from −3.2767 amps to+3.2767 amps volts in one-hundred-microamp steps.

Accordingly, for the six Raw Metrics (three for voltage and three forcurrent), allocating 12 bytes is sufficient.

The packets that result from the Raw Metrics can be structured asfollows:

Header Start Bytes 2 bytes 16 bits Receiver ID 1 byte 8 bits MessageType 2 bytes 16 bits Data V[RF] 2 bytes 16 bits A[RF] 2 bytes 16 bitsV[S] 2 bytes 16 bits A[S] 2 bytes 16 bits V[D] 2 bytes 16 bits A[D] 2bytes 16 bits Total 17 bytes 136 bits

The tradeoff between packetizing Battery Need Metrics versus Raw Metricsconcerns packet size (the greater the size, the greater the transmissiontime) versus computing cycles (the greater the computations, the higherthe load). Packetizing Battery Need Metrics saves on bytes transmitted,but pushes the calculations down to the receiver. The reverse is thecase with packetizing the Raw Metrics.

The Battery Rating Metrics (MaxChargeRate and StorageCapacity) areuseful for computing battery need. But the values of these parameterstend to change relatively slowly, so it would be wasteful for thereceiver to transmit these values as often as the fluctuating batteryneed values are transmitted.

The Battery Rating Metrics reduce slowly over months and years of use.As described above, these parameters may be periodically re-calculatedon the basis of careful receiver measurements or by using a simpleapproximation, for example a straight-line prediction based on calendardate.

A minimal Battery Rating Packet will contain these values:

Header Start Bytes 2 bytes Receiver ID 1 byte  Message Type 2 bytes DataMaxChargeRate 2 bytes [0 . . . 65535] mW StorageCapacity 2 bytes [0 . .. 65535] Wh 

Battery Rating Packets are sent to accommodate rare but importantupdates to these values. However, since these are rare packets, loadingthese special packets up with many fields can permit one multiple-usepacket to serve more than one purpose.

For example, periodic Battery Rating Packets could also contain manyother parameters about the receiver:

DeviceID specific device, perhaps a serial number Manuf manufacturer'sname Part# part number or SKU Lot lot number for tracking purposesRevision hardware/software revision level MAC special number forcommunications DeviceType CellPhone BatteryType Part# MaxChargeRate 2bytes 0 . . . 65535 mW StorageCapacity 2 bytes 0 . . . 65535 Wh

The receiver sends Battery Need Packets wirelessly to the transmitter.To do so, the receiver either uses a side-channel, or appends the packetto a beacon signal.

In a preferred embodiment, the receiver generates a beacon signal. Thepurpose of this signal is for the receiver to announce its presence tothe transmitter.

The beacon signal has many tight constraints on its timing, duration,and repetition rate. Every bit of data added to the length of the beaconsignal takes away from the time available for transmission of wirelesspower from the transmitter. Therefore, the smallest possible amount ofdata should be included with the ID portion of the beacon signal. In oneembodiment, the beacon is designed with minimal start bytes and nomessage type or data portion. A side-channel is used for the latter.

In yet another preferred embodiment, a side-channel is used for theentire Battery Need Packet. In an alternate embodiment, the Battery NeedPacket is sent with each beacon.

Battery Need Packets sent as a preamble to the beacon would be sent outevery time the beacon is sent. In a preferred embodiment, this frequencycan be approximately 10 milliseconds.

Packets sent out on a side channel have no beacon constraints, and couldbe sent at any frequency, including continuously—especially if thefrequency were altered from the frequency used by the transmitter todeliver wireless power to the receiver.

As noted earlier, Battery Rating Packets are sent at a much lowerfrequency than the Battery Need Packets (measured in seconds).

In one embodiment, the receivers send a BatteryFull message to thewireless power transmitter when full. This is an indication that thereceiver has no more need of the transmitter at that time, and wishesnot to burden the transmitter with further Battery Need Packets untilsuch need exists.

In another embodiment, when its battery is full, the receiver simplystops all communications to the transmitter. Then transmitter would thenpresume the receiver had left the area.

In both embodiments, when the receiver becomes aware of the need formore wireless power, it could pursue the normal introduction processthat all receivers must undertake when brought into the presence of atransmitter. Following this, the receiver would resume sending BatteryNeed Packets as described herein.

With a plurality of receivers wirelessly sending Battery Need Packets,the next step is for the transmitter to receive these packets.

The transmitter has at least one central collection point for receivingBattery Need Packets. This is a data controller within (or associatedwith) the transmitter. It receives the wireless Battery Need Packetsfrom none, one, or multiple receivers.

In a typical installation, there can be multiple wireless powerreceivers near at least one wireless power transmitter. Many receiverscan then transmit Battery Need Packets to the data controller.

Cross-interference between their multiple un-coordinated transmissionsmust be prevented. The packets can be coordinated by having the wirelesspower transmitter poll each receiver for the Battery Need Packet.Alternatively, multiple many-to-one messaging schemes are well known inthe art of data communications, for example CSMA-CD.

Generically, a radio transceiver in the data controller will becommunicating with the receivers. The transceiver receives data line andpresent signals to be resolved into bits by a data detector, possiblyrun through decryption circuitry, which exit as a stream of bytes. Thesebytes are shifted into a data input channel on a processor looking for aspecific series of bytes that make up the beginning of a data blockheader.

Typically, as discussed earlier, the header includes details like MediaAccess Control bytes (MAC addresses) or a Receiver ID, so the controllerknows which receiver sent the message. A final header byte typicallycodes the message type. Once this is found in the data stream, theremaining bytes take on meaning according to a protocol that lays outwhat the bits mean in that particular message type.

This packet unraveling approach is typical of many protocols, and thereare numerous examples in the art.

Once the message types are identified, the specific data parameters thatthose messages are designed to send can be recovered from the datastream.

Using Message Type from the packet header, the data controller canextract the specific encoded Battery Need (e.g. Raw Metrics or BatteryNeed Metrics, Momentary, Smoothed, or Predicted).

With the abundance of message types comes the possibility of varietiesof message types that are similar to one another, or that containsimilar kinds of data, but with different encodings, differenthigh-level meanings, or with different purposes.

The data controller must normalize this variable data into a common needformat. In a preferred embodiment, this common need format is TTD.

In one embodiment, all receivers transmit the Raw Metrics in the sameway, and with the same encoding, at all times, using the same messagetype. In this case, TTD can be calculated from these readings using theformulas described earlier.

In another embodiment, different message types could transmit the sameessential data, but with different encodings or higher-level meaningsfor the raw data represented at the low level by the Raw Metrics. Anexample would be all receivers using the same function (e.g. TTD) forbattery need, but some receivers sending the Raw Metrics, others sendthe Battery Need Metrics, and still others send TTD.

In this case, each receiver is sending complete information forcalculating the value of TTD. For Battery Need Packets containing TTD,no further processing is needed. For packets containing the Battery NeedMetrics, then TTD is calculated using the functions described earlier.For packets containing the Raw Metrics, the formulas described earlierare used for transforming these values into the Battery Need Metrics.Then the TTD function is applied to calculate the value of TTD.

In a third embodiment, different Receivers use incompatible groups ofmeasurements or implement special features that depend upon uniquecapabilities of custom receiver hardware or software. In these cases,there will have to be some means of normalizing the data.

For example, for a receiver that measures and communicates onlyDrainRate or StateOfCharge, the transmitter will need to makeassumptions about the missing data in order to normalize thosemeasurements into TTD. These assumptions can be drawn from manufacturerdata about the typical performance of the receiver battery.

With the Battery Need Packets received and normalized into commonreadings (preferentially TTD), the transmitter is ready to satisfy theseneed requests optimally.

With this invention, any kind of wireless power transmission approachcan be used, including:

-   -   phased microwave array like that developed by Ossia Inc.,        formerly OmniLectric, Inc.;    -   ultrasound like that developed by UBeam;    -   magnetic resonance like that developed by Witricity;    -   infrared laser like that developed by PowerBeam;    -   ambient energy harvesting like that developed by PowerCast; and    -   any other wireless power transmission technology.

The reason that this invention applies to all wireless transmissiontechnologies is that all such technologies are capable of deliveringpower via pulses. It may be that some of these technologies areconstrained in choice of pulse modification approach (e.g. frequencymodification instead of phase or time or directed transmitter).

But this invention applies to all means of generating at least twopulses of wireless power, each pulse being sent to one of two receiverslocated in different places.

However, the preferred embodiment, discussed next, employs phasedmicrowave array technology in the transmitter (as is described by OssiaInc., formerly Omnilectric, in U.S. Pat. No. 8,159,364), using phasefocused pulsing.

The ability to direct the power from multiple antennae of a phased arrayto a single receiver has many advantages. One advantage discussed hereis that of being able to direct specific amounts of power to differentreceivers based upon their needs.

It is well known in the art that electrical power can be sent as aseries of pulses. These power pulses are collected and smoothed by oneelectronic circuit to provide a constant source of power to anotherelectronic circuit.

By sending individual power pulses to different circuits that smooth thepulses, power from one source can be distributed to multiple destinationcircuits.

Proper pulse allocation is accomplished by sending the optimal number ofpulses to each individual receiver. Each receiver gathers power from thepulses that are sent to it, and thereby obtains the necessary power touse as needed.

When differing power requirements must be satisfied, each receiver canbe targeted with sufficient power pulses to meet that receiver'sspecific requirements. If all power pulses are the same size, receiversneeding more power (e.g. ones with a lower TTD) can receive more pulses,while receivers needing less power (e.g. a higher TTD) can receive fewerpulses. Other schemes can be employed if, for example, the power pulsesare of different sizes (e.g. individual pulses can be expressed asmultiples of the smallest pulse).

At the transmitter, before pulse allocations can be calculated, thepower needs of every receiver in the group of receivers must be known.

This information comes from the receivers themselves, and the collectedinformation permits calculation of the total power to be delivered aswell as the pulse allocations.

Now that the transmitter has collected what each of the receivers wouldwish to receive, it needs to distribute the pulses.

FIG. 7 shows an exemplary scheme 70 where the transmitter is configuredto communicate with four receivers, A, B, C, and F. The receiver A issending a beacon pulse 71, followed by receiver B sending two beaconpulses 72 and 73. Per each beacon cycle 74, the transmitter sends 4pulses to these receivers. For the first beacon 71, sent by A, there areno other receivers expressing battery need, so A receives all 4 pulses75. For the second beacon 72, sent by B, all four receivers areexpressing roughly equal battery need. So the transmitter sends fourpower pulses 76, 77, 78, and 79, to the four receivers, B A, C, and F,respectively. One power pulse goes to each of the four receivers.

In one embodiment, the transmitter sends, for example, 100 pulses perbeacon cycle. The transmitter allocates these 100 pulses amongreceivers. The number of pulses sent to each of these receivers can becalculated as follows:# pulses allocated to receiver i=round((need of receiver i/total need ofall receivers)*100)

Where need is expressed as TTD, a different allocating function isneeded. For example:

FUNCTION: TTD2PULSE

-   -   CONVERT LIST OF TTD VALUES TO LIST OF PULSE COUNTS    -   GIVEN INPUT ARRAY=TTD[1 . . . N]    -   CALCULATE OUTPUT ARRAY=NUMPULSES[1 . . . N]    -   NORMALIZE=SUM(TTD[1 . . . N])    -   WEIGHT[1 . . . N]=NORMALIZE/TTD[1 . . . N]    -   WEIGHTSUM=SUM(WEIGHT[1 . . . N])    -   PULSEFACTOR=WEIGHTSUM/MAXPULSES    -   NUMPULSES[1 . . . N]=WEIGHT[1 . . . N]*PULSEFACTOR

ALTERNATE LAST LINE:

-   -   NUMPULSES[1 . . . N]=MAX(1, WEIGHT[1 . . . N]*PULSEFACTOR)

This method allocates the pulses among the receivers according to theirrespective battery needs expressed as TTD.

The foregoing two allocation schemes are merely examples. This inventionaddresses any other approach to allocating available pulses to thereceivers according to the respective battery needs of the receivers.

The wireless power data controller and transmitter coordinate withmultiple receivers to deliver power to them. The following sectiondiscusses one embodiment of a transmitter interacting with none, one ortwo receivers according to this invention.

Receivers are able to detect when they get power bursts from thetransmitter. Each power burst contains multiple power pulses. Each pulsecan be directed to one among multiple receivers. One preferredembodiment has, for example, 100 power pulses per burst, but any ratiois acceptable under this invention.

FIG. 8 shows a power burst 81 comprising of a large number of powerpulses in the burst, say 100. We will consider, for example, 26 of thesepower pulses feeding 9 receivers. Receiver #1 receives 4 power pulses82, Receiver #2 receives 7 pulses 83, and Receiver #9 receives 3 pulses84. As has been described, this discrepancy of pulse allocation amongthe receivers is due to the different degree of Battery Needs of eachreceiver.

The power pulses contain energy directed to a specific receiver, but notevery power burst needs to contain power pulses for every activereceiver. In other words, a particular receiver can be left out of apower burst by not having any power pulses allocated to it within thatparticular burst.

The transmitter uses a side channel to communicate beacon requests tothe receivers. These requests ask the receivers to identify themselvesand to begin declaring their need for power.

All receivers within the transmitter range will receive all beaconrequests. But each beacon request is directed exclusively to a singlereceiver. This is accomplished by using a unique Receiver ID in themessage. Each receiver within range examines whether a particular beaconrequest is addressed to it or not.

If there are two receivers requesting power at the same time, conflictsneed to be avoided. This is accomplished by having each receiverdisregard one beacon request and respond to the next. For example, withtwo receivers, one receiver can skip the even requests, while the otherreceiver skips the odd requests.

In the examples below, it is assumed that the receivers are sendingtheir respective Battery Need Packets as part of their beacons. As notedearlier, this approach is one embodiment of the invention. In otherembodiments, a side channel on the receiver sends out the Battery NeedPackets independent of the beacons.

Let us consider first a simple case where there are no receivers nearbya transmitter. A simple corresponding scheme 90 for this case isdepicted in FIG. 9. A lone wireless power transmitter 91 broadcasts aseries of general announcements (the “Regular Announcement”) 92 at timeintervals 93 (e.g. five-second time intervals). Expecting that it willeventually discover a nearby receiver, the transmitter sends a RegularAnnouncement 92 from a single antenna 94, called “Proxy”. The specialantenna Proxy 94 is part of a cluster of antennae 95 in the transmitter91. Regular Announcements 92 are to be received by potential receiver“Client” 96. The communication scheme 90, is considered as an examplecase where there are either no receivers present, or where present oneshave no power to respond. In both cases, there are no returning signalsfrom receivers.

FIG. 10 shows another example of transmitter-receivers communication. Ina communication scheme 100, a client receiver 96 finally does appear inthe environment; it receives the “Regular Announcement” 92, waits arandom amount of time, “Random Hold Off” 101, and then responds with an“I'm hungry” message 102. In this communication scheme 100, thetransmitter determines (from the contents of the “I'm hungry” message)that the sender is not authorized to receive power. In this case, thetransmitter 91 replies with a “can't help you” message 103. The clientreceiver 96 receives this message and marks that transmitter and itsconfiguration revision level as non-responsive. This prevents the clientreceiver 96 from needlessly contacting the transmitter 91 again, untilit has been reconfigured. (A reconfiguration could be due to a newauthorization for the receiver to receive power).

FIG. 11 shows another example of transmitter-receivers communication.The communication scheme 110 depicts a successful introduction of aclient receiver 96 into the transmitter's list of authorized receivers.As before, the receiver receives the “Regular Announcement” 92, waits arandom amount of time, “Random Hold Off” 101, and responds with an “I'mhungry” message 102. With this receiver, the transmitter 91 determinesthat the receiver is, in fact, authorized to receive power. When this isthe case, the transmitter 91 replies with a Receiver ID picked from apool of available Receiver IDs. Once this Receiver ID is selected,(order is irrelevant, they simply must be different), it declares to thereceiver that, for example in the communication scheme 110 shown in FIG.11, “You are Client #3” 111.

The receiver receives this message and returns a “My Story” message 112.In one embodiment, this message is a Battery Rating Packet. This packetis compiled and sent by receivers only upon being assigned a Receiver IDby the transmitter 91.

Once the transmitter 91 receives this packet, it determines how to treatthe receiver, and sends a “Send Beacon” message 113 to it.

The exemplary communication scheme 120 shown in FIG. 12 describes a casewhere a successfully authorized client receiver 96 interacts withtransmitter 91 that has no other receiver within reach.

Having received the transmitter's “Send Beacon” message 113, the clientreceiver 96 sends a first beacon 121. The first beacon 121 allows everyantenna in the transmitter array to determine the exact phase angle ofthe receiver's signal at that antenna. This enables every antenna in thetransmitter 91 to capture that phase information, and calculate acomplex conjugate of the phase angles for each antenna in the cluster.Later, these phase angles can be used to transmit a single pulse ofwireless power 122 from all those antennas back to that receiver.

The phase angles of all the returning transmissions from all the antennaelements have been arranged so they all peak as they travel through thelocation of the receiver's receiving antenna (and by design, nowhereelse). This provides a pulse of power to the receiver, which hascircuitry designed to harvest the energy and derive power from it.

Once the receiver detects that it has received one or more power pulsesin a burst, it then sends out a second beacon 123, and later receivesanother power burst 124. This interaction continues until thetransmitter 91 stops delivering power bursts.

Once a receiver in “Send Beacon” mode detects a missing power pulse, itwaits for a different “Send Beacon” command 125 from the transmitterProxy. The “Send Beacon” command 125 means “send one beacon” and it alsohas a skip factor. The skip factor commands the receiver to not respondto every power pulse with a beacon, but to skip some number of powerpulses before sending a beacon.

Now, we consider the case of having at least two receivers waiting forbeacon requests. In the communication example 130 shown in FIG. 13, thecommunication starts by the interaction between one transmitter 91 andone client receiver 131 called “A”. Client receiver A, 131 has detecteda power burst 132, and has sent a beacon signal 133 requesting anotherburst—with a 0 skip factor.

The transmitter 91 discovers it is time to send out another “RegularAnnouncement” 134. A second client receiver B 135 (for example Receiver#6) that receives the “Regular Announcement” 134 will delay a randomamount of time, “Random Hold Off” 101 and then respond with a “I'mhungry” message 102 message to that request.

At this point, the transmitter 91 determines that the second clientreceiver B 135 is also authorized to receive power pulses. So, thewireless transmitter 91 picks another Receiver ID from the free ReceiverID pool and it uses the Proxy 93 to send a “You are Receiver #6” message136.

During this time, client receiver A 131 sends a beacon message 133,expecting another power burst in response. Because the transmitter issetting up the second client receiver B 135, this beacon is ignored. Theclient receiver A 131 will notice the missing power burst and changemodes. Instead of sending beacons without being asked, this new modewaits for beacon requests before sending them. The new mode will alsoskip a configurable number of beacon requests before responding.

Back at the second client receiver B 135 (Receiver #6) which has justreceived the “You are Receiver #6” message 136, it responds by providingits own “My Story” message 137. Once this packet from the second clientreceiver B 135 (Receiver #6) has been received, the wireless powertransmitter 91 now has two active client receivers; client receiver A131 and client receiver B 135 that need to be supplied with power, andboth are waiting for beacon requests.

Continuing with the communication example 130 shown in FIG. 13, justafter the point where the transmitter 91 has requested and received abeacon request from each of the two active client receivers (clientreceiver A 131 and client receiver B 135), the two beacons have set upthe phase relationships of all the antennae, so the power pulses can bedirected to either receiver as desired. Both receivers are waiting forpower pulses (from somewhere in a power burst), and both are expectingto disregard their first power burst and not return a beacon. This is asif they both think they are first in line.

A way is needed to get one receiver to go ahead of the other receiver,so one will return beacons for odd bursts and the other for even bursts.Otherwise, they will both respond to odd (or even) bursts, and theirbeacons will interfere. One way to get one receiver to ignore a burst isto have no pulses in that burst for that receiver. So, shown in FIG. 13,an entire power burst is directed exclusively to client receiver A 131,which will detect a pulse and will skip sending a beacon in response.The second client receiver B 135 (Receiver #6) has received no powerpulses in that power burst, so detects no pulses, it continues waitingfor a first power burst. The second client receiver B 135 (Receiver #6)is still ready to skip the first power burst it sees.

Next, a second power burst is sent containing power pulses 138 for bothclient receiver A 131 and the second client receiver B 135 (Receiver#6). Both receivers consult their skip status, with client receiver A131 finding it has already skipped enough, (once) and the second clientreceiver B 135 (Receiver #6) finding is has not yet skipped. So thewireless power transmitter receives a beacon from client receiverA131—now skipping odd power bursts. Subsequent power bursts will beeither even or odd, and will receive a beacon from client receiver A 131or the second client receiver B 135 (Receiver #6) based on the skipfactor of one they both have been commanded to use.

Skip factors greater than one can be used. With three Receivers, forexample, a skip factor of two will let each Receiver skip sendingbeacons when either one of the other two are sending beacons. Thisscheme can work with multiple receivers, but depends upon trouble-freereception of beacons from each receiver.

In another alternative embodiment, receivers and transmitters caninteract by having the transmitter request beacons from the receivers ofwhich it becomes aware, rendering no skip factor necessary. Receiverresponds to a “Regular Announcement” with a data packet describingitself (“My Story”). A specific beacon request naming that receiver canaddress it whenever the transmitter decides. Once the receiver respondswith a beacon, it will receive power from pulses inside subsequent powerbursts. This is a less efficient protocol, because time must be spentasking each receiver to send a beacon, rather than having them all waittheir turns.

In a preferred embodiment, the normalized Battery Need data provided tothe transmitter by the data controller is TTD. This allows thetransmitter to compare the receivers according to TTD, includingMomentary TTD, Smoothed TTD and Predicted TTD.

In an alternative embodiment (the “1BitDirective”), the need data iseither a one “1” or a zero “0”. “1” corresponds to more power(“MorePower”); and “0” to less power (“LessPower”). This alternativeembodiment loses some degree of information on battery need, but gainson the preferred embodiment due to reduced complexity.

In the 1BitDirective, the receiver monitors the sign (+ or −) of thestorage battery current, and requests MorePower when the current isflowing out from the battery; LessPower when the current reading isflowing into the battery.

In addition, the receiver will request LessPower when MaxChargeRate isexceeded and when StateOfCharge is “full” (e.g. 100% or over 90%).

The receiver's task can be expressed in Program Design Language (PDL) asfollows:

If BatteryCurrent > 0 Then    If BatteryCurrent > MaxChargeRate Then      Request “LessPower”    Else       If StateOfCharge = Full Then         Request “LessPower”       Else          Request “MorePower”      Endif    Endif Else    Request “MorePower” Endif

The above code increases demand for power until MaxChargeRate isexceeded or the StateOfCharge is full. This will occur regardless ofvariations in the DrainRate. The code snippet needs to be run only onetime per beacon. An electronic circuit could ready implement this codeusing circuit design techniques known in the art.

A minimal packet contains only what it must, including the Start Bytes,Receiver ID, and possibly one or two message types. The message typeswould be pre-assigned numbers. Usually these numbers refer to a specificlayout of the data section of the message.

One possibility is to have a layout with one bit in the data section.This one bit would carry the MorePower or LessPower directive.Alternatively, the header can employ message layouts with no data bitsin the data section. Instead, the message type itself carries theMorePower or LessPower directive.

The packets comprise one or more of StartBytes, ReceiverID's,MessageTypeBytes, and DataBytes.

Start bytes: This could be, for example, 2 bytes containing “0xA55A”,which might be an uncommon enough sequence.

Receiver ID byte: This Receiver ID could be anything unique. In IEEE 802format, let us presume a particular Receiver had 01:23:45:67:89:AB. Butthat kind of ID is too long for a beacon. The protocol described earlierallows for a Receiver ID to be assigned by the wireless powertransmitter. One byte can uniquely identify over 200 Receivers. For thisexample, the byte “0xAB” has been selected.

Message Type: This would be two bytes that were assigned to communicatethe 1BitDirective layout. An efficient way is to have MorePower andLessPower versions of some unrelated often-used message type.Alternatively, let message type 0x62 be the message type for1BitDirectives that have one bit of data in the layout.

Data Bytes: In the alternative 1BitDirective embodiment, the packetcontains Data Bytes. Since the minimum count is likely one byte, we canencode MorePower as “0x01” and LessPower as “0x00”. This more thancarries the one bit of information needing to be sent.

The entire example 1BitDirective message (in hexadecimal) is: “A5 5A AB62 01”

This message breaks out as two Start Bits, “A5” and “5A”, followed bythe Receiver ID (assigned by the wireless power transmitter) of “AB”,and then by the Message Type of “62”. The #62 message type is known tohave a single byte containing a single bit at the least significantposition (rightmost). Code to extract message 62 is as follows:

MorePower=(“0x01”==Payload(0))

Payload is the byte array received from the data portion of the receiverbeacon. There is only one payload byte, at offset zero. If Payload isequal to “0x01” then RequestedMorePower is True. Otherwise,RequestedMorePower is False (because it actually requested LessPower,which is the equivalent in this scheme).

The summary of what the packet says is:

Receiver# Receiver ID of receiver communicating MorePower True/False onwanting MorePower

This information is fed into a transmitter that tracks the requests ofeach receiver.

If the 1-bit more/less signal is sent by the receiver with every beacon,the result can be thought of as similar to a pulse-width-modulatedfeedback signal.

In Program Design Language (PDL) format, the transmitter executes thefollowing procedure:

For Each Receiver       If MorePower[Receiver]          IncreaseNumberOfPulses[Receiver]       Else          DecreaseNumberOfPulses[Receiver]       Endif Next Receiver

NumberOfPulses[Receiver] is the number of power pulses the transmitteris currently allocating to Receiver.

One embodiment has, for example, 100 beacons per second and 100 pulsesper beacon cycle from all the receivers in the area. (Any other count ispossible; 100 is picked as an easy-to-calculate example.)

With 100 beacons per second, a single receiver could request MorePower.In response, the transmitter would smoothly ramp power from zero to 100pulses per second. Suitable protections could prevent “Increase” and“Decrease” code from exceeding the 100 pulse allotment. With for example20 competing receivers, each could cover the entire range within 5seconds, in this example. This is quite adequate response time.

Once the transmitter knows the NumberOfPulses each receiver has beenallocated, and provided that the total of the pulses allocated(“TotalPulses”) is less than or equal to the pulses available, thetransmitter allocates the pulses as follows:

Pulse = 1 For Each Receiver    For (I=0; I<NumberOfPulses[Receiver];I++)    PulseForReceiver[Pulse++] = Receiver Next I Next Receiver

This starts allocating pulses from the first power pulse in the burst.The code walks through the list of receivers, allocating to eachsubsequent receiver the number of pulses assigned to that receiver.

The 1BitDirective approach to pulse allocation can also be called “Rampand Dither”. For example, after a cell phone had been left unusedovernight near a transmitter, the morning would find the battery fullycharged. NumberOfPulses would be dithering up or down very near zeropower at the receiver.

When the cell phone is turned on in the morning, battery current wouldimmediately be flowing out to the cell phone circuitry, resulting inMorePower requests.

These requests would continue until the transmitter power level rosesufficiently to exceed the demand from the receiver's electronics, atwhich time requests for LessPower would occur.

At the transmitter, the NumberOfPulses for that receiver would ramp upto a certain value and then dither at a level supplying power just asneeded. If the ramping process had taken too long, the StateOfChargewould no longer indicate “Full” and additional MorePower requests wouldresult until StateOfCharge returned to “Full”.

At the transmitter, TotalPulses may be more than the total available(e.g. 100 pulses in the above example). Several approaches for reducingthe requested total are possible.

One approach divides TotalPulses by a factor, say 100 to obtain a“division factor”. Then NumberOfPulses for each receiver is divided bythat factor to determine the actual number of pulses to be sent. Thisstarves all receivers equally, which may be problematic for somereceivers.

It also would not be long before all starved receivers are asking forall 100 pulses. This could result in all receivers receiving the sameamount of power, which also may be problematic for some receivers.However, for example, twenty receivers getting 1/20th of the total ofthe wireless power available is a reasonable response.

Another approach would be to have a code that repeatedly passes throughthe list subtracting one from every receiver's allocation until thetotal was 100. A 10 msec burst of power pulses could then be sent out,in this example.

An improvement would be to not allow any receiver's allocation to dropbelow 1 pulse. A further improvement would be to not demote theallocations of those units that have no internal storage, such as alocal battery. This “no battery” status would be known for each receiverand could be tested with something like “CanDemote” code;

While TotalPulses > 100    Receiver = Next(Receiver)    If TotalPulses >100 Then       If CanDemote[Receiver] Then          Pulses[Receiver] =Max(1, NumberOfPulses[Receiver]−1)          RecalculateTotalPulses      Endif    Endif Wend

This will starve all the receivers that can be demoted, but equally so.The receivers with no internal storage will have all the power theydemand, which is a necessary response. One downside is that thereceivers will all take longer to re-charge their batteries, resultingin a graceful failure mode.

However, a transmitter surrounded by an RF absorbing environment andmany hungry receivers will be overwhelmed and may even allow somereceivers to discharge if their DrainRate is high enough. There could besome indication to the transmitter owner that the transmitter is beingcalled upon to provide more power than it can.

The embodiment of the invention that employs Predicted Battery Need iscapable of far richer analysis than the other embodiments describedabove. Once predicted use is relied upon by the transmitter, rather thanrecent use (e.g. Momentary Battery Need and Smoothed Battery Need),specific, differentiated characteristics of the receivers becomes moreimportant.

The discussion below explores additional parameters for describing thesedifferent receiver characteristics, as well as a classification ofreceiver types by power use. The purpose of this information is toenable the transmitter to develop a rich model of the collection ofreceivers it serves.

The chief benefit of performing this rich predictive modeling anddepending on this modeling for allocating pulses within power bursts isto reduce the amount of computation needed by the transmitter on eachcycle of power burst delivery.

The drawback of depending on a priori models of receiver power usearises when the actual usage deviates significantly from the model.

Beyond the Battery Need Metrics and Battery Rating Metrics describedearlier, predictive modeling is optimized by using additionalparameters.

The Predictive Parameters described below are sufficient to schedule aseries of power pulses to be sent to various receivers and providecustomized levels of power to each one. When these parameters areavailable to the transmitter from all the receivers, the values can beused by the transmitter to determine the best allocation of theavailable power pulses.

Each receiver will receive a number of power pulses sufficient to powerthe receiver and to recharge the battery (if there is one) to cover theexpected short-term future usage, within the predicted time thatreceiver is expected to still receive wireless power, regardless ofbattery size or present level of charge, but at a safe rate ofre-charge.

Some receivers are mounted on walls near a transmitter at all times.Other receivers, particularly portable ones, will not have access towireless power in remote locations and be used there. Some portablereceivers only have access to wireless power for a short time per day;others may have regular overnight access.

The following Power Availability Parameters characterize the access areceiver has to wireless power:

Wireless Power Available [. . .] minutes/day Average Duration ofWireless Power Access [. . .] minutes Number of Power Access Sessions [.. .] per day.

Preferably, these parameters are also collected and maintained in thereceiver itself.

Some wireless power receivers draw little power; others draw much power.Some receivers draw power continuously because they are in operationevery minute of the day; others draw power only when a person is usingthem, or when a sensor (or other receiver) activates them. Thosereceivers using power intermittently will typically have short or longsessions of power draw; the remainder of the time they draw very lowstandby power, or no power.

The following Power Draw Parameters characterize wireless powerreceivers power draw:

Typical Power Draw [. . .]Watts For [. . .] minutes/day Average Durationof Typical Power Draw session [. . .] minutes Number of Power DrawSessions [. . .] per day

Preferably, these parameters are measured and maintained in the receiveritself, and sent on-demand to the transmitter for use in planning theallocation of power pulses.

Some receivers may wish to manage the power coming from the transmitter,so additional Demand Parameters can be included.

Please provide this level of power now [. . .]Watts Transmitter to useits discretion [Y/N]

In one approach, a convention is established whereby the requested powerlevel is a demand with an “N” in this field, but with “Y” in the field,the transmitter can select the power level provided to the receiver.

Different classes of receivers, classified by power availability anddraw patterns, tend to generate different classes of PredictiveParameters.

Receivers with no means to store power themselves must be suppliedsufficient power at all times by a wireless power source. The locationsof these receivers must be known to the source at all times, so thatwireless power can be directed to their locations. The location datamust be retained by the transmitter even after main power has beeninterrupted for a protracted period, such as during a power failure.Therefore, all location information for fully dependent receivers willinvolve non-volatile memory storage in the transmitter. These receiverscan be identified by the “Total Energy Storage Capacity” parameter,which would typically be zero. An example is an electric water pumpkeeping water in pipes warm by recirculating water through the waterheater.

Receivers that must always be in service must also be suppliedsufficient power at all times by a transmitter or large backup battery.This is a class of receiver similar to the Fully Dependent Receiver,except these would typically have local energy storage to power abeacon—in order to ensure the receipt of power from the transmitter whenit is available. A possible example is an oxygen concentrator (medicalreceiver to aid in breathing) with a battery backup to ride throughpower failures.

Exhausted Receivers are those receivers which have already drained theirpower reserves and have been forced to shut down. These receivers willreceive a high power pulse priority in order to recharge quickly, butwill need a special treatment.

The special treatment is required because normally, a beacon signal sentby a receiver will be received by a nearby wireless power source, whichwill then respond by transmitting power to that receiver's location.These are typically portable receivers, so their location is not known.An exhausted receiver has no available power to generate a beacon, andtherefore no nearby transmitter can become aware of the receiver.Instead of a beacon “moving the power to the receiver”, the receivermust be moved to the power.

In this case, the receiver with no reserve power will be handled byhaving at least one specific location always provided with wirelesspower. When an exhausted receiver is placed in this “resurrection spot”,wireless power is provided to it until it is able to produce a beacon.At this point, if use of the receiver is demanded immediately, it can beused while being charged as long as it remains within reach of awireless power source. It is anticipated that the transmitter willprovide sufficient power to both charge and power the receiver while itis within range, even if it is a receiver needing high power along witha quick-charge requirement.

Receivers having nearly exhausted their power reserves will begin to becharged when they enter the wireless power field. This will occur whentheir beacon signal is detected by a transmitter able to supply power tothe receiver. Power supplied to these receivers will have a priorityover other receivers that have sufficient power to operate. The PresentReserve Capacity parameter is important for these receivers, so they canbe provided with a quick-charge power pulse train.

Receivers having high power requirements must be allocated more powerslots from the available power pool than receivers needing little power.As the technology matures, providing larger amounts of power will becomepossible. Receivers with high continuous power requirements such as ahair dryer will need stable allocations during use. When the transmitteris providing power near the limit of its capacity, some receivers cantolerate varying power levels, and will have their loads shed from thetotal power output as needed. A good example of this is an electric carcharging in a garage. A bad example is a hair dryer that appears torandomly fall back to cooler settings in order to accommodate a wirelesspower source's limited capacity. (The hair dryer would likely beconsidered defective by most users.) The “Typical Power Draw” parameteris key in identifying these receivers. The hair dryer may also wish toassert, for example “Please provide 1000 W now, no discretion” status.

Some receivers receive continuous use, such as a radio or a TV left onat all times. As before, stable allocations of power slots will need tobe provided for these always-on receivers. The “Average Duration ofTypical Power Draw Session” will be important in identifying thesereceivers.

Some receivers receive heavy use throughout the day, others of the samemake and model receive little use. Take the case of two identical cellphones, one owned by a stock-broker nearly always on the phone, theother owned by a retired person. Both could arrive together at apublic-access transmitter having batteries with 50% of their capacityremaining. This could represent 4 hours of reserve capacity to one, and4 days of reserve capacity to the other. The receivers not only reportreserve capacity, but the level and minutes/day of typical use. Withthis information provided to the transmitter, both could leave togetherwith 80% reserve capacity in their respective units—even though thestock broker's phone received much more power.

Some receivers have limited or intermittent usage patterns. A TV remotemay face heavy and yet intermittent usage for a few hours per day. Astud-finder may face light use every few years. These sorts of receiversmay be best re-charged only after a certain level of discharge has beenreached. Some battery technologies—NiCad in particular—do not respondwell to being kept on a charger continuously. Suitable algorithms usedby the transmitter can manage these batteries, charging them whennecessary.

In some homes, a household intercom might not get much use. If thedesigners expected the unit to use wireless power, a very small batterysufficient only to get out one or two beacons could be used. A “Pleaseprovide 100 mWatt now” update could be sent whenever the unit was calledinto use.

An electroluminescent night light with no battery could be kept lit, andvarying the average number of power pulses provided per second couldprovide control over the brightness.

Motion sensors and wall clocks do not move out of the wireless powerfield.

In the case of a vacuum cleaner stored in a shed without wireless powernearby, the wireless power receiver unit could turn on the beeper whenthe battery needed recharging. It could then be brought into the house(near the wireless power source) and recharged, even while being used.The power pulse allocator would note for example, a low “Wireless PowerAvailable 0 minutes/day” and a “Present Reserve Capacity 4%”, andcalculate a suitable high-power rush, limited by “Maximum continuouscharge rate for this battery”.

For receivers stored in remote locations, a Status Repeater could allowthe receiver to send its battery charge level to the transmitter. (Therepeater would only retransmit data to the wireless power transmitter,not retransmit power to the receiver.) The transmitter would then notifythe user that the remote receiver requires charging. The remote StatusRepeater might use power line communications or WiFi to communicate withthe transmitter along with the same radio communications technology thatthe transmitter uses to communicate with the receiver.

While this invention has been described in terms of several embodiments,there are alterations, modifications, permutations, and substituteequivalents, which fall within the scope of this invention. Many ofthese modifications can also be practiced alone or in differentcombinations.

It should also be noted that there are many alternative ways ofimplementing the methods and apparatuses of the present invention. It istherefore intended that the following appended claims be interpreted asincluding all such alterations, modifications, permutations, andsubstitute equivalents as fall within the true spirit and scope of thepresent invention.

What is claimed is:
 1. An apparatus comprising: means for determining,based on a charging need of an energy storage device of at least oneclient receiver of a plurality of client receivers positioned distallyfrom, and not in physical contact with, any part of the apparatus, anallocation among the plurality of client receivers for transmission ofwireless power signals to the plurality of client receivers via at leasttwo antennas of a plurality of antennas associated with the apparatus;and means for directing the at least two antennas to transmit thewireless power signals according to the allocation to at least twoclient receivers of the plurality of client receivers by modifying atleast one of: phases, transmission frequency, timing, amplitude, anddirection, of the at least two antennas.
 2. The apparatus of claim 1,further comprising means for directing at least one antenna of theplurality of antennas to receive, from the at least one client receiver,a signal encoding data representative of the charging need of the energystorage device.
 3. The apparatus of claim 2, wherein the means fordirecting is configured to direct the at least one antenna to receive,from the at least one client receiver, a beacon signal including thedata representative of the charging need of the energy storage device.4. The apparatus of claim 2, wherein the data representative of thecharging need of the energy storage device includes one or more metricsincluding at least one of: a state-of-charge, a drain-rate, and areceived-power, of the energy storage device.
 5. The apparatus of claim2, wherein the data representative of the charging need of the energystorage device is encrypted, the apparatus further comprising means fordecrypting the data representative of the charging need of the energystorage device.
 6. The apparatus of claim 1 further comprising theplurality of antennas.
 7. The apparatus of claim 6 further comprising anantenna array including at least some of the plurality of antennas. 8.The apparatus of claim 7, wherein the antenna array comprises a phasedtransmission array.
 9. The apparatus of claim 1, wherein the means fordirecting is configured to direct the at least two antennas to transmit,according to the allocation, the wireless power signals as pulses to theat least two client receivers.
 10. A system comprising: a plurality ofantennas; and a controller configured to: determine, based on a chargingneed of an energy storage device of at least one client receiver of aplurality of client receivers that are positioned distally from, and notin physical contact with, any part of the system, an allocation amongthe plurality of client receivers for transmission of wireless powersignals to the plurality of client receivers via at least two antennasof the plurality of antennas; and direct the at least two antennas totransmit the wireless power signals according to the allocation to atleast two client receivers of the plurality of client receivers bymodifying at least one of: phases, transmission frequency, timing,amplitude, and direction, of the at least two antennas.
 11. The systemof claim 10, wherein the controller is further configured to direct atleast one antenna of the plurality of antennas to receive, from the atleast one client receiver, a signal encoding data representative of thecharging need of the energy storage device.
 12. The system of claim 11,wherein the controller is further configured to direct the at least oneantenna to receive, from the at least one client receiver, a beaconsignal including the data representative of the charging need of theenergy storage device.
 13. The system of claim 12, wherein the beaconsignal encodes data representative of a location of the at least oneclient receiver, the controller further configured to cause the datarepresentative of the location to be stored in memory communicablycoupled to the controller.
 14. The system of claim 11, wherein the datarepresentative of the charging need of the energy storage deviceincludes one or more metrics including at least one of: astate-of-charge, a drain-rate, and a received-power, of the energystorage device.
 15. The system of claim 11, wherein the datarepresentative of the charging need of the energy storage device isencrypted, the controller further configured to decrypt the datarepresentative of the charging need of the energy storage device. 16.The system of claim 10 further comprising a phased transmission arrayincluding at least some of the plurality of antennas.
 17. The system ofclaim 10, wherein the controller is further configured to direct the atleast two antennas to transmit, according to the allocation, thewireless power signals as pulses to the at least two client receivers.18. The system of claim 10, wherein the controller is further configuredto determine the allocation based on a predictive model.
 19. The systemof claim 10, wherein the controller is further configured to normalizedata representative of charging needs of energy storage devices of atleast two client receivers of the plurality of client receivers.
 20. Oneor more non-transitory computer readable media having programinstructions stored thereon which, when executed by one or moreprocessors of a machine, direct the machine to: determine, based on acharging need of an energy storage device of at least one clientreceiver of a plurality of client receivers that are positioned distallyfrom, and not in physical contact with, any part of a structureassociated with the machine, an allocation among the plurality of clientreceivers for transmission of wireless power signals to the plurality ofclient receivers via at least two antennas; and direct the at least twoantennas to transmit the wireless power signals according to theallocation to at least two client receivers of the plurality of clientreceivers by modifying at least one of: phases, transmission frequency,timing, amplitude, and direction, of the at least two antennas.